Protection of polished metal surfaces



March 25, 1969 ca. c. WIGGINS 3,434,904

PROTECTION OF POLISHED METAL SURFACES F'i'led Oct. 27, 1965 INVENTOR.

AWTOR/Vf 45 United States Patent PROTECTION or PoiIsIiED METAL SURFACES Glenn C. Wiggins, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed Oct. 27, 1965, Ser. No. 505,438

Int. Cl. B3211 7/06, /08

US. Cl. l56-306 3 Claims This invention relates to the protection of polished metal surfaces and more particularly to a process for temporarily protecting such surfaces with a flexible, weather resistant, self-anchoring laminate film structure composed of a chloroethylene polymer and a metallic foil.

The problem of protecting polished or finished metal surfaces has greatly increased in recent years with extensive use of stamping and bending of pre-plated sheet metallic stock used in the sheet metal fabrication of household appliances and the like. In such fabrication process it is highly desirable that any protective covering is applied continuously to a plated or finished surface, and is readily removable therefrom without resort to special tools, solvents or the like.

Prior known methods for protecting polished or plated metallic surfaces include the spraying of suspensions of rubbery synthetic resins or asphaltic products, and allowing the carrier to evaporate, whereby a layer of the protective substance is deposited upon the finished surface. Such method, however, requires sufficient time for spraying of the surface and for drying of the carrier prior to performing shaping operations upon the protected material. Further, such protective coatings generally require the use of solvents and/or abrasion for removal from the metallic surface.

Another method comprises clipping of the surface to be protected into such substances as synthetic latex, vinyl aromatic hydrocarbons, ethyl cellulose, polyvinyl alcohol and shellac. It has been found, however, that all of the above methods require substantial time in application and subsequent removal.

Still another method contemplates the coating or covering of the polished metal surface with gummed or pressure sensitive adhesive tape. The principal difficulties e11 countered with such materials are the prohibitive high cost and the tendency to leave a deposit of adhesive upon the protected surface following removal of the protective tape.

Yet another method comprises the extrusion of relatively high molecular weight hydrocarbon polymers such as polyethylene and the like, at high temperatures, directly onto the substrate surface to be protected and thereafter immediately combining the substrate and polymer coating by pressure. Such methods, however, generally provide variable bonding with accompanying formation of undesirable discontinuous coatings.

In an attempt to avoid the above difficulties, use has been made of certain synthetic, resinous sheeting material, to which has been applied, and which is capable of retaining, and electrostatic charge, as the protective coating or covering for the polished metallic surfaces. In such process (as described in the US. Patent No. 3,054,708, issued Sept. 18, 1962) the electrostatic charge is placed upon the sheeting or film prior to its subsequent application upon the finished metallic surface or simultaneously with its application to such surface. A major difliculty encountered herein is the necessity for the application of such electrostatic charge to the protective material which is, at best, difiicultly applied in a uniform manner under varying atmospheric conditions. Further protective coatings of this type, are subject to extensive deterioration and degradation with resulting loss of adresinous, flexible sheet material capable of adhering uniformly to a metallic surface, but which. may be readily removed therefrom without difliculty and without resort to other than ordinary skill.

Another object is to provide a protective sheet material as described herein, which is resistant to the adverse effects of sunlight.

Other and related objects will become apparent from the following description and claims and the annexed drawing which schematically illustrates an embodiment of the invention.

In accordance with the present invention, polished or finished metal surfaces are effectively and efficiently protected by contacting the same with a continuous selfanchoring laminate film structure having a thickness of between about 0.0005 and 0.1 of an inch and composed of a chloroethylene polymer film joined in intimate lamination with a sunlight resistant metallic foil, preferably Where such metallic foil has a thickness of from about 0.00025 to about 0.003 of an inch, wherein the chloroethylene polymer portion of such laminate film structure is contacted with the polished metal surface while utilizing pressures sufficient to remove essentially all of the air from between the laminate film structure and the metallic surface being protected. The protective laminate film may thereafter be removed when desired without difliculty and without resort to special equipment or other than ordinary skill.

The chloroethylene polymers, i.e., those polymers having chlorine pendant from the polymer chain such as the polymers of vinyl chloride and vinylidene chloride, and particularly the normally crystalline vinylidene chloride polymers, i.e., those polymers of vinylidene chloride containing at least about 70' weight percent of vinylidene chloride in the polymer molecule with any remainder being an ethylenically unsaturated comonomer such as vinyl chloride and the like, have been found to be particularly useful for application to polished metal surfaces due to their good bonding characteristics, toughness and ability to be easily removed from the surfaces being protected. Such polymers have further been found to be easily laminated to thin metallic foil materials such as aluminum foil, steel tinplate, plated steel foil and the like, by passing self-supporting layers of such polymeric film and metallic foil through pressure rollers heated to a temperature below the decomposition point of the polymeric film.

Referring to the drawing, FIGURE 1 schematically illustrates a typical installation for the application of the composite film structure 10 comprising an inner layer of a chloroethylene polymer 11 and an outer layer of a metallic foil 12, to a roll of sheet material 13 having at least its outer surface plated or otherwise finished. The metal is moved over a plurality of horizontally disposed rollers 14 which support the metal in a plane, The protective laminate film material, as described herein, is supported above the surface of the metal at the nip of rollers 15 and 16 under a pressure suficient to eliminate essentially all of the air from between the protective sheet material and the surface of the metal to be protected.

After application, the laminated metal and protective sheet 17 may be fed to a take-up roll wherein the metal is again re-packaged for shipment and subsequent use. The protective material of the present invention will adhere very effectively to the metal surface even during those processing operations requiring deep-drawing and sharp bending; such adhesion resulting, at least in part, from the exclusion of essentially all of the air between the protective sheet and the metal surface to be protected. Upon completion of the herein described operations, it is necessary only to manually strip the protective material from the protected surface. As no adhesive has been employed during the application of the protective material, the protected surface will, upon removal of such protective material, exhibit a clean, unmarred appearance requiring no further treatment. Further, the sheet 17 may be exposed to direct sunlight for extensive periods without resultant undesirable degradation of the chloroethylene polymer constituent of the protective laminate film structure.

The following specific example serves to illustrate the effectiveness and advantages of this invention, but is not to be construed as limiting its scope.

EXAMPLE The following results were obtained using apparatus essentially as illustrated in the drawing, wherein a sheet of polished chrome-plated steel 0.01 inch thick and about nine inches wide having a finished surface was fed through the nip of a pair of smooth variable speed driven rollers having a diameter of about 6 inches and operating at a rate of about 15 feet per minute. An oriented sheet (prepared using standard bubble techniques and having a thickness of about 0.001 of an inch composed of a copolymer of 73 percent by weight vinylidene chloride and 27 percent by Weight vinyl chloride, and, additionally, formulated with about 8 percent by weight dibutyl sebacate as a plasticizer and 0.2 percent magnesium oxide; said sheet being in essentially coextensive lamination with an aluminum foil having a thickness of about 0.001 of an inch was fed into the nip of the rolls mentioned above, as a protective layer on the finished surface of the sheet metal. A laminated structure was thereby formed composed of a continuous, adherent, oriented polymeric protective covering on a steel sheet, wherein substantially all of the air had been excluded from between the protective layer and the surface being protected. Such protective layer was found to be desirably adherent to the finished surface of the steel sheet even during deep-drawing and sharp bending manipulations of the protected sheet and was essentially impervious to the degradative effects of sunlight following extensive exposure thereto, i.e. there was no evident of undesirable loss of adhesion of the protective coating following exposure of the laminate structure to direct sunlight for 4 a period of six weeks. The proective coating was, however, easily peeled from the surface of the steel sheet before or after re-winding of such protected steel sheet, to provide a clean, unmarred, polished steel surface requiring no further treatment.

Similar good results were also obtained wherein the metal contacting surface of the herein described protective sheet was passed over a means for ionizing the air next to such surface (to remove any residual electrostatic charge from the surface of the sheet) prior to deposition to the finished metal surface at the nip of the pressure rolls.

Further, equally good results were obtained utilizing the processes as described above wherein polished aluminum sheet metal having a thickness of about 0.038 of an inch was utilized.

Similar good results, as described herein, are obtained utilizing any of the protective laminate film structures as prescribed by the present invention.

What is claimed is:

1. In the method of temporarily protecting a polished metallic surface with a synthetic, resinous, flexible sheet material, the improvement consisting of: contacting said polished metallic surface with a flexible laminate film structure composed of an inner layer of a chloroethylene polymer and an outer layer of a metallic foil, said laminate film structure being essentially free from electrostatic charge, wherein said chloroethylene polymer portion of said laminate film structure is applied to said polished metal surface under pressure sufficient to remove essentially all of the air from between said laminate film structure and said polished metal surface.

2. The method of claim 1 wherein said laminate film structure has a thickness of between about 0.0005 and 0.1 of an inch.

3. The method of claim 2 wherein said chloroethylene polymer is a normally crystalline copolymer containing about 73 weight percent vinylidene chloride and about 27 weight percent vinyl chloride and said metallic foil is aluminum foil.

References Cited UNITED STATES PATENTS 2,120,461 6/1938 Copeman 29-423 2,679,969 6/ 1954 Richter.

3,054,708 9/1962 Steinberg 156272X 3,075,868 1/1963 Long 156-244X 3,152,950 10/1964 Palmquist et al. 16l214 3,191,286 6/1965 Armstrong et al. 29-424 3,354,015 11/1967 Klusmire et a1. 156306 DOUGLAS I. DRUMMOND, Primary Examiner.

US. Cl. X.R. 161-216, 406 

1. IN THE METHOD OF TEMPORARILY PROTECTING A POLISHED METALLIC SURFACE WITH A SYNTHETIC, RESINOUS, FLEXIBLE SHEET MATERIAL, THE IMPROVEMENT CONSISTING OF: CONTACTING SAID POLISHED METALLIC SURFACE WITH A FLEXIBLE LAMINATE FILM STRUCTURE COMPOSED OF AN INNER LAYER OF A CHLOROETHYLENE POLYMER AND AN OUTER LAYER OF A METALLIC FOIL, SAID LAMINATE FILM STRUCTURE BEING ESSENTIALLY FREE FROM ELECTROSTATIC CHARGE, WHEREIN SAID CHLOROETHYLENE POLYMER PORTION OF SAID LAMINATE FILM STRUCTURE IS APPLIED TO SAID POLISHED METAL SURFACE UNDER PRESSURE SUFFICIENT TO REMOVE ESSENTIALLY ALL OF THE AIR FROM BETWEEN SAID LAMINATE FILM STRUCTURE AND SAID POLISHED METAL SURFACE. 